A fork in no way solves this because you can't for the devs who mozilla is paying. Firefox is a huge project requiring devs with lots of experience in the technology who also like to be compensated. You can't fork firefox, you have to change the leadership or nothing else will change.
It's related to funding, but recognition is really important. Actually forking (as opposed to the GitHub fork button) is generally seen to be hostile and and will split the community (see e.g. ffmpeg vs. libav). This means that getting a fork to succeed is much harder than it would have been for the original project. For example if the Mozilla foundation went after government grants and donations for funding Firefox instead of trying to monetize the browser they'd probably have much more success than any unproven fork could ever dream for.
